Picoampere Current Measurements by On-Chip Amplifier
Original Publication Date: 1985-Jan-01
Included in the Prior Art Database: 2005-Feb-18
The test circuitry measures leakage currents of integrated circuit devices by using on-chip device amplifiers to extend the low-current range from microamperes to picoamperes. Measurement accuracy is practically independent of test circuit device characteristics and AC noise. Shown in Fig. 1 is a pair of IGFETs, Q1 and Q2, made, e.g., from first level metallization over two adjacent base diffusions. The resulting current switch configuration measures the time needed to charge-up capacitor C1 by leakage current IL, through a suitable voltage range. The time required is translated to a corresponding voltage across C2 whose charging rate can be further controlled by adjusting constant current source I. The IGFET subcollectors can be tied to pad P1 or to another positive supply. Fig. 1 circuit operation follows: 1.